As a dual Israeli-American citizen, there is also the question of whether Mr Fischer's nationality could hamper his chances, as the top IMF job usually goes to a European.

Economist Nouriel Roubini said Mr Fischer was a perfect candidate but would find it difficult to derail Ms Lagarde's campaign. "At this late stage, he does not have enough support to succeed," he said.

Mohamed El-Erian, co-chief investment officer at Pimco, the world's largest bond fund, also praised Mr Fisher's credentials. "He is extremely well liked by the staff of the IMF, well known and genuinely respected by the member countries of the institution."

On Sunday, G20 member Indonesia backed Ms Lagarde for the role, the first public endorsement from a major emerging market. This was closely followed by that of Egypt.

Europe has come out in force for Ms Lagarde, as it struggles to keep the IMF-led bailouts of Greece, Ireland and Portgual on the rails.

The United States and Japan, the IMF's other power brokers, remain publicly uncommitted.

The pullout of two other potential candidates - Grigory Marchenko of Kazakhstan and Trevor Manuel of South Africa - underscores the widespread belief that Europe already has a done deal.